Hot-water generator



Nov. 16, 1954 T. H. F. STIEBEL HOT-WATER GENERATOR 4 Sheens-Sheet 1 Filed Feb. 16, 1952 JNVENTOR O H./:' S TIE BEL UPNE Y Nov. 16, 1954 Filed Feb. 16, 1952 FIG. 2

4 Sheets-Sheei 2 I My s5 s3 2 5a JNVENTOR THEODOR HEST/EBEL Nov. 16, 1954 T. H. F. STIEBEL 2,694,768

HOT-WATER GENERATOR Filed Feb. 16, 1952 4 Sheets-Sheet 3 FIG. 4

JNVENTORA THEOD R HEST/EBEL YORNEY United States Patent HOT-WATER GENERATOR Theodor H. F. Stiebel, Holzminden (Weser), Germany Application February 16, 1952, Serial No. 271,905 Claims priority, application Germany February 17, 1951 16 Claims. (Cl. 219-39) This invention relates to hot water generators, and more particularly to the structural features of such generators of the instantaneous flow type in which the volume and the temperature of the emitted hot water are maintained substantially at selected predetermined constant amounts.

Hot water generators of the most varied construction are prior known, the most prevalent electrically heated type comprising a tank having an internal heating element, appropriate waterways and fittings, and switches for connecting and disconnecting the heating element. On opening the water intake faucet, water flows through the tank and is heated by the heating element. In the gas heated types, the water flows through a system of pipes over which the heated gas passes. Connection and disconnection of the electrical heating element occurs simultaneously with the opening and closing of the water emission faucet, for example, by a mechanical coupling, by the hydraulic pressure, or by a temperature responsive device, etc., or occurs independently by operating a switch. With gas heated hot water generators, the usual practice is to employ the hydraulic pressure so that on opening the water emission faucet a membrane permits the inflow of a heating gas which ignites on contact with a pilot flame.

For a given amount of applied heat and for a given volume of water heated thereby, a definite temperature will be attained by the volume of water, as follows from natural laws and the heating efficiency. Again, for a given hydraulic pressure, the volume of water which is desired may readily be controlled by varying the crosssection of the fiow. Thus in an electrically heated, hot water generator, for example, on the application of some 18 kw. to the heating element of a through flow type generator some ten quarts of water per minute at a temperature of 105 degrees F., are delivered. On decreasing the rate of delivery, the temperature of the delivered r water correspondingly increases, while on an increase in the delivery rate the temperature correspondingly decreases.

The quantity of water delivered, given a constant crosssection of flow, depends on the hydraulic pressure which, in a water supply system having a plurality of relatively closely adjacent tapping points, is subjected to noticeable variations. Assume that a hot water generator is being used for a shower, for example, or a small type for washing hands, and is adjusted by opening its emission faucet so that the temperature of the delivered water is about 105 degrees F. If now a tapping point adjacent thereto is opened, the hydraulic pressure applied to the hot water generator is decreased and, without any change in the faucet opening, the volume of water delivered decreases. But with the quantity of heat applied remaining unchanged, the temperature of the smaller volume of water delivered increases, and the user of the hot water generator may scald himself quite badly. Assume that now the user appropriately changes the faucet opening, and thereafter the other tapping point is closed. Now the pressure and the volume of the delivered water will rise, the temperature of the delivered water will fall, and a new setting of the faucet opening becomes necessary.

Similar undesirable phenomena occur when mixed water is drawn from the mixing chamber of a hot water generator constructed as a hot water reservoir. In the case of a low pressure hot water reservoir, for example, cold water coming from the mains displaces hot water out of the reservoir into the overflow and then into the mixing chamber. In the mixing chamber this hot water from the tank is mixed, as determined by the setting of the mixing cock, with other cold water from the mains. If the hydraulic pressure suddenly decreases, not enough hot water is displaced from the tank since the flow cross-section remains the same, and hence the temperature of the mixed water falls. In many situations, adjustment of the faucet opening once it has been set is quite burdensome.

The need for protecting the hot water generators of the prior art and the heating element in electrically heated hot water generators from overheating requires leaving some water in the container at all times. When the drawing of water is stopped, the container contents are hot, but this hot water is not immediately used. And where the hot water generator is not insulated, the contents cool and hence the expended heating energy is wasted. In such types therefor the endeavor is to make the water compartment as small as possible.

Hot water generators are frequently used in place of the common faucet whether it be for washing or for general kitchen purposes. Prior known hot water generators are of such large construction that their adaptation to such use is rarely possible.

It is an object of the invention to provide an electrically heated instantaneous hot water generator in which the volume of the emitted water is automatically and uniformly controlled by the hydraulic pressure under which cold water from the mains is supplied to the generator.

A further object of the invention is to provide, in an electrically heated, through flow, hot water generator, an additional control of the volume of water emitted which control is actuated by the temperature of the emitted water.

A still further object of the invention is to provide means in the waterways of an instantaneous hot water generator by which the cross-section of a portion of the waterway is automatically variable in a continuous manner by the pressure of the water flowing thereinto and therethrough.

Still a further object of my invention is to construct an instantaneous hot water heater of maximum compactness of which the hollow container has a water compartment of minimum volume and also houses the automatic control elements.

I accomplish the foregoing, and other obvious, objects by providing an electrically heated, hot water generator having a compact, small dimensioned, hollow container inthe walls of Which I embed the heating element and in the interior of which I house the elements for automatically and uniformly controlling the volume of the emitted hot water. Water from the mains is caused to act on a spring biased bellows to actuate a control member which in turn acts both upon the electrical switch for the heating element as well as upon a variable portion of the cross-section of the Waterway to control the quantity of water admitted to the water compartment for heating. The heated water overflows from the top of the water compartment into the hot water outlet, which may be provided wih a cross-sectional portion which is variable by a rotary motion manually imparted but is preferably automatically controlled by the temperature of the emitted water.

An illustrative embodiment of the electrically heated, hot water generator of the instantaneous flow type of my invention, together with certain modifications thereof, are described below with the aid of the accompanying drawings in which:

Figure 1 shows, in partial section, an elevational side view of an illustrative embodiment of the instantaneous hot water generator of my invention which is electrically heated and has an automatic and stepless pressure control of the volume of the emitted hot water;

Figure 2 is a top view of the embodiment of Figure 1 with the cover removed;

Figure 3 shows the details of the mercury switch support;

Figure 4 is an elevational section through the inlet faucet integral with the angular Water supply fitting;

Figure 5 is an elevational section through the hot water emission faucet and its variable spray head;

Figure 6 is a partial section of a modification of the pressure control of Figure 1 employing a slide valve;

Figure 7 is an elevational simplified section of a modification in which the temperature of the emitted water controls the volume of the emitted water; and

Figure 8 is a section along line 88 of Figure 7.

Within the hollow container 1 is inserted a heating spiral 2 having the connector terminals 3a and 3b for connecting a line supply of electricity, the outer diameter of the heating spiral being of such magnitude that it is substantially equal to the internal diameter of the container 1. A second, and smaller, hollow container 4 is inserted within the heating spiral, the outer diameter thereof corresponding substantially to the inner diameter of the spiral. The second container 4 has a large bent over flange 5 which is tightly soldered at its rim portion to container 1, the connector terminals 3a and 3b extending through the flange. By such construction, the water compartment of the instantaneous flow hot water generator formed by the space between the two containers, is kept at a minimum.

The hollow interior of the second container 4 is closed by the cover 6. From the bottom 7 of the second container the pipe 8, soldered to such bottom, extends into the interior of the second container. Within the pipe 8 is housed a cylindrical bellows 9 having a top 10, which may also close the top of pipe 8 as shown, and a bottom 11 which is a sliding fit within the pipe Sand is normally flush with the lower open end of pipe 8, for example. A spring 12, tensioned by a hollow screw 13 passing through the bellows top 10, is mounted within the bellows. Threaded through the bellows bottom 11 and soldered thereto so as to be Watertight, a control rod 14 extends in both directions and is guided by the hollow screw 13. Both end regions of the control rod are threaded, as at 15 and 16, and the control rod in turn serves as a guide for the spring 12.

The bottom 17 of the external container 1 has a central opening 18 and is bent over, and within the bent over portion a flanged bushing 19 extends outwardly from within the container, a formed bushing 20 being threaded up on the extending portion of the bushing 19 so that the region therebetween of bottom 17 is engaged by both, which are then soldered to the bottom 17. Bushing 19 has a cylindrical bore while the bushing 20 has a registering bore of which at least a portion thereof is a conical bore 21, the control rod 14 extending through both bores. A conical plug 22 is threaded upon the threaded end region 16 of the control rod to such extent that the plug is adapted to register with the conical bore 21 but is normally at a predetermined distance therefrom. By means of the threaded clamp nut 23, the bushing 20 is screwed to the upwardly extending branch of an angular fitting 24 with an intermediate packing 2'5. A specially shaped, knurled nut 26 is threaded onto the threaded end region 15 of the control rod. One horizontal branch of the three-branched angular fitting 24 is adapted to be coupled to the cold water supply, while a second horizontal branch thereof houses the water inlet valve (Figure 4) below described.

As best shown in Figure 3, the nut 26 has a forked member 2'7 to which there is connected a U-shaped member 28 by means of a pin 29. The U-shaped member 28 is supported by pin 30 on the supporting bracket 31 which in turn is fastened to cover 6 of second container 4. Both the ends of both the pin 29 and 30 are swedged over to assure that they will not fall out. Pivotable U- shaped member 28 has atfixed thereto, as by screwing, a bentdplate 32 to which the mercury switch 33 is fastene A terminal strip 34 (see Figure 2 for the clearest detail) is aflixed to the cover of the second container 4, and in the cylindrical wall portion of the container 1 above the cover 6, both a cable box 35 and a lamp 36 are attached and extend therethrough. Two wires of the three-wire current supply cable 37 are connected to the terminal strip 34, while the ground wire thereof is connected to the grounding terminal 38. From the terminal strip one of the current supply wires is connected to the heating spiral terminal 3a directly, while the other supply wire is connected to terminal 3b thereof by way of mercury switch 33. Lamp 36 is connected in parallel to the terminals 3a and 3b.

The instantaneous hot water generator is closed by the cover 39 held in place by the screw 40. The second,

container 4 is indented longitudinally at one region so as to provide room for the hot water overflow pipe 41 which opens at the top just below the cover 6 and at the bottom into the fitting 42 soldered into another opening in the container bottom 17. Fitting 42 has the longitudinal internal bore 43 which provides a water passageway to the water emission faucet 44, and has also the transverse bore 45 which is covered by the elastic ring 46 thus providing an emergency safety outlet for the water, respectively steam, should excessive pressures develop in the generator. Water emission faucet 44 is screwed to the fitting 42 by the cap nut 48, and by means of lock nut 49 the spatial position of the faucet 44 may be adjusted. The quantity of water flowing from the faucet 44 may be controlled and hence also the temperature of such emitted water. An adjustable spray head 50 is threaded to the water emission faucet 44, its object being to break the emitted water up into a spray. The cross-sectional area of the passage through which water flows to be emitted by faucet 44 may be manually varied as below described. Both the water supply angle.

fitting 24 and the control faucet 44, excepting their respective handles as well as the cold water supply pipe and the hot water spray head, are enclosed by the hood cover 51 held in place, for example, by the nut 52 on an extension of the supply faucet 24.

Referring to Figures 4 and 5, the water supply angle fitting (24 of Figure 1) has a main body casting 53 having the water passageways 54 and 55. A water closure valve 56 is provided in body 53, and the passageway 54 is connected to the water mains while passageway is connected to the water compartment of the instantaneous hot water generator, with the valve 56, operable by hand lever 57, connecting and diconnecting the passageways to each other. The water emission faucet (44 of Figure 1) has a body 58 into which fits a choke cock 59 dependent on the position of which more or less water is emitted from the generator. Variation in the position of the cook 59 is effected externally by means of hand knob 60. From cock 59 water flows through channel 61 to the spray head 50 which is threaded onto the body 58 of the emission faucet and comprises a threaded fitting 62' having a bore 63 of predetermined size and a flat surface portion 64. A disc 65 having an eccentrically positioned bore 66 is pressed by spring 67 against the flat surface 64. Spring 67 is supported upon a perforated plate 68 which is part of the metal housing 69, which in turn is bent over and rotatably supported on the shoulder 70 of the fitting 62. A perforated plate 71 extends across the bottom of metal housing 69.

In operation, when the valve 56 is opened by hand lever 57, water flows from the mains through the angle fitting '24 into the water compartment of the instaneous, through flow, hot water generator along the turns of the spiral heating element 2 and through the overflow tube 41 and the water emission valve 44 and spray head 50. If the volume of water emitted from the spray head be less than the volume of water flowing into the water compartment of the generator, a dynamic pressure is built up and the bellows 9 is compressed against the tension of spring 12. Thus the control rod 14, connected to bellows bottom 11, is moved upwardly and tilts the mercury switch 33 so that its contacts close the electric line supply circuit. The angle of tilt of the mercury switch from its normal disconnect position to its initial connect position is such that for even relatively small hydraulic pressures, that is for relatively small upward movement of the control rod, the mercury switch will definitely close th e line circuit. That the switch do not close the circuit immedlately upon initiation of the upward movement of the control rod is a safety precaution for when very small hydraulic pressures prevail in the mains sucha small volume of water is delivered to the generator water compartment that were the heating spiral energ1zed, the small volume of water in the compartment would readily be converted into steam. In addition, this arrangement permits the initial flow of cold water from the generator thus eliminating all possibility of scalding pending proper temperature adjustment by the user. Then on operation of the knob 60, the choke cock 59 opens the cross-section of the emission passageway to such extent that the volume of emitted water is substantlally equal to the volume admitted to the generator water compartment, and substantially no dynamic hydraulic pressure is produced. If the choking of the flow by water control faucet 44 is insuflicient to obtain practically boiling water from the generator, then a further choking of the outflow is had by means of the spray head by rotating the metal housing 69 to vary the degree of registration of bores 63 and 66. With the upward movement of the control rod 14, the conical plug 2'2 is drawn into the conical bore 21 and thus reduces the water entrance cross-section depending on the magnitude of the upward motion. The configuration and dimensions of th plug 22 and the bore 21 are of such predetermined order, and their relative position so predetermined, that at all times the desired volume of water is admitted to the generator water compartment. This arrangement thus acts as a pressure reducing valve and renders the inflowing volume of water independent of the pressure in the water line. When the inflow of water is shut oil, the pressure within the container 1 decreases and the compression spring 12 restores the cylindrical bellows 9 to its original position, while the control rod 14 pulls the mercury switch 33 back into the disconnect position.

In the modification shown in Figure 6, a cylindrical plug 72 is threaded upon the lower threaded end portion 16 of the control rod 14 in place of the conical plug 22 of the embodiment of Figure l, and slides in a perforated cylinder 73 closely fitted about it so that in accordance with the position of the control rod, a lesser or greater number of the perforations of cylinder 73 are covered to prevent, or are uncovered to permit, water to pass into the generator water compartment. The mode of operation thereof is similar to that above described for the embodiment of Figure 1, except that the magnitude of the cross-section permitting the flow of water is determined by the number of uncovered perforations.

A further modification in which the temperature of the emitted water, rather than the hydraulic pressure, is used to attain the desired control features is shown in Figures 7 and 8. A temperature responsive element, for example the bi-metal strip 74, is positioned in the path of the emitted water and is aflixed at an end region to the metal housing 69. An iris shutter 75, consisting of a plurality of sickle or are shaped elements 80 each of which has a pin 81 at one end, is pivotally supported by pins 81 in an annular plate 82 afiixed to the lower surface of the fitting 62. The free end of each element 80 likewise has a pin 83, the plurality of pins being arranged to form a circle. Each pin 83 passes through and is controlled by a radial slit 84 in an annular and rotatable plate 85. The rotatable annular plate 85 is provided with a pin 77 on which acts a tension spring 76 attached to a hook 7 integrally connected to the metal housing 69. The thermally responsive bimetal strip 74 lies below the rotatable annular plate 85 and is appropriately thermally influenced by the stream of water after the latter has successively passed through bore 63, fixed annular plate 82, the cross-sectional area uncovered by elements 80 of the iris shutter 75, and the rotatable annular plate 85. As has been stated, one end region of the bimetal strip 74 is aifixed to the housing 69, but its free end rests against pin 77 of the rotatable annular plate 85. When the temperature exceeds a predetermined amount, the free end of the bimetal strip will thus thermally respond, and in bending bears against the pin 77 and rotates the rotatable annular plate 85 against the pressure of the spring 76, guided in an appropriate cylindrical guide 86, in such manner that the cross sectional area uncovered by the iris elements 80 will become greater. Hence the volume of water passing therethrough will also become greater, which means that the temperature of the water must decrease for the same quantity of heat, the volume of water being now greater. When the temperature of the emitted water falls on continued withdrawal of water, the bimetal strip will tend to restore thus permitting the plate 85 to rotate in the opposite direction under the influence of spring 76 thereby decreasing the cross-section uncovered by the iris, and thus causing the temperature of the emitted water to rise.

What I claim is:

1. Hot water generator of the type in which water is heated during its flow therethrough comprising a first container, a closed second container within the first container of which the external wall is spaced from the first container, an electric heating element of spiral configuration within the space between the two containers and occupying a substantial portion of such space, the container walls and the exterior of the spiral forming a water compartment, an inlet passageway connected to substantially the lowermost region of the compartment and adapted to connect the compartment to an external supply of water under pressure, an outlet waterway at the region of the compartment substantially remotest from the inlet passageway, a normally open electrical switch within the first container adapted on closure to connect the heating element to a source of electrical potential, a valve within the inlet passageway normally open a predetermined amount, and means within the second container and extending into both the first container and the inlet passageway and responsive to the instantaneous pressure of the water supplied from the external source to actuate both the switch and the valve respectively to close the switch and to vary the predetermined amount of opening of the valve in such direction that the total quantity of water infiowing per unit of time remains substantially constant.

2. Hot water generator in which water is heated during its flow therethrough comprising a first vertical hollow cylinder having a closed bottom, a second vertical hollow cylinder having a closed bottom coaxially within the first cylinder, the diameter and the height of the second cylinder being less than those of the first cylinder, the cylinders being axially so positioned that there is a space between their bottoms, a tightly wound spiral electrical heating element of circular cross-section between the cylindrical walls and occupying a substantial portion of the space therebetween, a water inlet connection through the bottom of the first cylinder into the space between the cylinder bottoms, a water outlet from substantially the highest region between the cylinder walls, a switch adapted to connect the heating element to a source of electrical potential, a valve within the water inlet connection operable to vary the flow of water into the space between the cylinder bottoms and about the heating element between the cylindrical walls to a minimum, and means responsive to the hydraulic pressure in said space to actuate the switch to connect and the valve to maintain at a constant volume the inflow of water.

3. Hot water generator comprising a hollow container, an electrical heating means within the container, a water compartment within the container, an inlet passageway connecting the compartment externally to a source of water under pressure, an electrical circuit including a switch within the container adapted to connect the heating means to a source of potential, a first valve within the inlet passageway, means responsive to the water pressure within the compartment for actuating the switch and the first valve, an outlet waterway from the compartment remote from the inlet passageway, a second valve in the outlet waterway, and a means thermally responsive to the water flowing in the outlet waterway to control the degree of opening of the second valve.

4. Hot water generator according to claim 3 in which the thermally responsive device comprises a bimetal strip in the flow path of the water of the outlet waterway and having a free end region, an iris shutter positioned across the outlet waterway and having a predetermined opening for all water temperatures below a minimum, a stop on the shutter, and a spring tending at all times to engage the stop to the free end region, the strip being so disposed as to open the shutter more on an increase in temperature above the minimum and to permit the spring to move the stop to close the opening progressively on a decrease in water temperature.

5. Hot water generator comprising a hollow container, an electrical heating means within the container, a water compartment within the container, an inlet passageway connecting the compartment externally to a source of water under pressure, an electric circuit including a switch within the container adapted to connect the heating means to a source of electrical potential, a first valve within the inlet passageway, means responsive to the water pressure within the compartment for actuating the switch and the first valve, an outlet waterway from the compartment remote from the inlet passageway, and a second valve in the outlet waterway comprising a pair of discs positioned transversely across the outlet waterway, an eccentrically positioned bore in each disc in the direction of water flow, one disc being rotatable relative the other disc to vary the degree of opening of the second valve.

6. Hot water generator comprising. a hollow container, an electrical heating means within the container, a water compartment within the container, an inlet passageway connecting the compartment externally to a source of water under pressure, an electric circuit including a switch within the container adapted to connect the heating means to a source of potential, a first valve within the inlet passageway, means responsive to the water pressure within the compartment for actuating the switch and the first valve, an outlet waterway from the compartment remote from the inlet passageway, a faucet terminating the outlet waterway, a cold waterway from the source of water under pressure terminating in the faucet, a second valve in the cold waterway at the faucet termination thereof, and means thermally responsive to the mixed water emitted by the faucet for controlling the degree of opening of the second valve.

7. Hot water generator in which water is heated during the i'low therethrough comprising a first vertical hollow cylinder having a closed bottom, a second vertical hollow cylinder having a closed bottom positioned coaxially within the first cylinder and longitudinally with their tops registering, the diameter and height of the second cylinder being less than those of the first cylinder, a helical heating element of a plurality of turns of circular cross-section between the cylindrical walls and occupying a substantial portion of the space between the cylinders, the cylinder walls and bottoms forming with the exterior of the heating element a water compartment, a water inlet to the bottom of the compartment, a water outlet from an uppermost region of the compartment, a manually operable normally closed first valve in the water inlet, a second valve in the water inlet beyond the first valve in the flow direction and normally open a predetermined amount, an electrical circuit including a normally open switch adapted to connect the heating element to a source of electrical potential, and means within the second cylinder and extending into the compartment and connected to the second valve responsive to the pressure of water in the compartment and adapted on opening the first valve to close the switch and to reduce the opening of the second valve from the predetermined amount on an increase in such pressure and on a reduction of the pressure below that corresponding to the predetermined opening of the second valve to open the switch irrespective of the closed or open position of the first valve.

8. Hot water generator according to claim 7 in which the means responsive to the pressure of the water comprises a hollow vertical tube having its lower open end afirxed to the bottom of he second cylinder, the tube extending coaxially with and within the second cylinder, a closure member across the top end of the tube, a flexible air-filled bellows within the tube having an upper end fixed to the closure member and a vertically movable lower end normally fiush with the bottom of the second cylinder, a coiled spring in the interior of the bellows tending to restore the lower end of the bellows to the flush position on displacement of the lower end, and an actuating member integral with the movable end of the bellows extending through the bellows and therebeyond upwardly to the switch and extending below the movable end into the second valve.

9. Hot water generator according to claim 7 in which the upper end region of the cylindrical wall of the second cylinder is bent outwardly and at the top edge region is connected to the top edge region of the cylindrical wall of the first cylinder there to close the annular space therebetween and thus the water compartment, a hollow cylindrical cover is fitted into the open end of the second cylinder, the switch is a mercury contact switch and is supported on a rocker housed within the hollow cover, the means responsive to the pressure of the water comprises a hollow vertical tube having its lower end open and afiixed to the bottom of the second cylinder, the tube being wholly within the second cylinder, a closure member across the top end of the tube, a flexible air-filled bellows within the tube having an upper end fixed to the closure member and a vertically movable lower end normally substantially flush with the bottom of the second cylinder, a coiled spring within the bellows tending to maintain the movable end of the bellows in the flush position, and an actuating member integral with the movable end of the bellows extending upwardly through the bellows and the second cylinder into the hollow cover and connected to the rocker to tilt the switch to closure on upward movement of the actuating member, the ac tuating member also extending downwardly into the sec-- ond valve to decrease the opening thereof on upward movement of the actuating member.

10. Hot water generator according to claim 7 in which the means responsive to the pressure of water in the compartment is an air'filled bellows having a movable end directly exposed to the water in the compartment, a tension spring within the bellows adapted to maintain the movable end in a predetermined normal position, and an actuating member integral with the movable end of the bellows, the actuating member being connected to the switch to actuate the switch to closure on movement of the movable end of the bellows against the tension of the spring and to maintain closure of the switch for all increased movement of the movable end of the bellows against such spring tension and for as long as the spring is tensioned, the actuating member being also connected to a movable portion of the second valve uniformly to reduce the opening thereof on such movement of the movable end of the bellows against such spring tension from a predetermined amount to a minimum.

11. Hot water generator according to claim 7 in which the means responsive to the pressure of the water in the compartment is an air-filled bellows having its movable end in the compartment, a tension spring adapted to maintain the movable end of the bellows in a predetermined position, and an actuating member integral with the movable end of the bellows, the actuating member. being connected to the switch to actuate it to closure on movement of the movable end against the tension of the spring and to maintain switch closure for all further movement of the movable end against such spring tension and for all time the spring is tensioned, the actuating member being also connected to a movable portion of the second valve stepwise to reduce the opening thereof on such movement of the movable end of the bellows against spring tension from a predetermined amount to a minimum.

12. Hot water generator according to claim 7 in which a third valve in the water outlet is normally open and is settable to vary the cross-section of the water outlet to obtain water of the desired temperature of a range of high temperatures from the water outlet on successive openings of the first valve.

13. Hot water generator according to claim 7 having a third and normally open valve in the water outlet, the third valve being settable to the opening corresponding to a desired temperature from the range of high temperatures of which the generator is capable during an open condition of of the first valve for any number of succeeding openings after closures of the first value, and in which the means responsive to the pressure of the water in the compartment comprises an air-filled bellows having amovable end directly operable by the water pressure in the compartment, a tension spring adapted to maintain the movable end in a predetermined position, and an actuating member integral with the movable end, the

actuating member being connected to the switch to actuate the switch to closure on a predetermined amount of movement of the movable end against the tension of the spring and thereafter to maintain switch closure for as long as the spring is tensioned, the actuating member also being so connected to the second valve to reduce the opening thereof on all movement of the movable end against tension of the spring from a predetermined amount to a minimum.

14. Hot water generator in which water is heated during its flow therethrough comprising a first vertical hollow cylinder having a closed bowed bottom, a second vertical hollow cylinder having a cloced bowed bottom coaxial with the first cylinder, the diameter and the height of the second cylinder being less than those of. the first cylinder and the top edges of the cylinders being substantially coplanar, a coiled electrical heating element of circular cross-section between the cylindrical walls and occupying a substantial portion of the space between the cylindrical walls, the bottoms and cylindrical walls of the cylinders forming with the exterior of the heating element a water compartment of smooth spiral configuration, a water inlet to the bottom region of the compartment adapted to connect a source of water under pressure tothe compartment, afirst' normally closed valve in the water inlet operable to the open position from exterior the first cylinder, a second normally open valve in the water inlet beyond the first valve in the direction of water flow into the compartment, means responsive to the hydraulic pressure prevailing within the compartment on opening the first valve to reduce the opening of the second valve toward a minimum on increase of the pressure beyond a predetermined range, the range being the normal range of pressure variations of the source of water, a water outlet from the upper region of the compartment, and a third valve normally open in the water outlet, the opening of the third valve being adjustable to control the temperature of the water emitted by the outlet.

15. Hot water generator according to claim 14 in which the pressure responsive means actuates a switch to connect the electrical heating element to a source of electrical potential when the pressure in the compartment reaches the lowest value in the predetermined range and maintains the switch closed for all pressures above such lowest value and opens the switch when the pressure decreases below such lowest value of the predetermined range.

16. Hot water generator for delivering hot water at constant temperature irrespective of hydraulic pressure variations, comprising a hollow container, electrical heating means within the container, a water compartment within the container, an input passageway to the compartment adapted to connect the compartment to a source of water subject to pressure variations, an output water passageway from the compartment, a switch adapted to connect the electrical heating means to a source of electrical potential, a manually operable, normally closed, first valve in the output passageway, a manually operable, normally closed, second valve in the input passageway, a hydraulic pressure responsive valve in the input passageway at a region thereof in the direction of flow beyond the second manually operable valve, the hydraulic pressure responsive valve being normally open to a predetermined cross-section within the input passageway, and means interconnecting the switch and the hydraulic pressures responsive valve whereby on opening the manually operable first and second valves the hydraulic pressure responsive valve closes the switch and maintains the switch closed for all variations in the hydraulic pressure above that corresponding to the predetermined crosssection and simultaneously varies the open crosssection in the input passageway in accordance with the instantaneous hydraulic pressure variations above the pressure corresponding to the predetermined cross-section in such manner as to maintain constant the volume per unit of time of water flowing through the compartment and out of the output passageway.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,198,073 Simon Sept. 12, 1916 1,419,225 Colebrook June 13, 1922 1,494,326 Adams May 20, 1924 1,920,284 Wells Aug. 1, 1933 2,347,122 Peet Apr. 18, 1944 2,380,132 Walther July 10, 1945 

